Process of chemically transforming photographic images



Patented Septo 3, 1935 attain PROCESS CHEMICALLY TRANSFORMINGPHOTOGRAPH-[IO WAGES Friedrich Lieu-g, Dresden, Germany No Drawing.Application April M, 1930, Serial No. 444,359. In Germany April 1-7,1929 2 Claims.

This invention relates to a process of chemically transformingphotographic images.

In order to transform the silver of photographic images into othercombinations only such 5 photographic processes are known up to now inwhich the silver of the photographic image has been transformed, by wayof the ferricyanide process or by means of oxidizing or halogenizingreagents, into other combinations by which may be produced tone images,intensifications of theoriginal silver image or dye images'in case theobtained parts possess mordanting action. However if it is desired toutilize, in place of the reduced silver image, the silver halideresidual image, the possible ways of transforming the same are-small ifit is not first reduced, because according to the known processes it canbe transformed into silver iodide or brown silver sulphide only.

The present process, now, opens up new possibilities of obtainingchemical compounds by way of the photographic silver image, or of thesilver halide residual image, in a very simple manner, the said imageshitherto being incapable of being converted at all into these compounds,or

only in a very complicated manner.

The essential feature of the process according to the invention consistsin subjecting the image forming substance for instance AgBr, AgCl to theaction of complex forming solvents, chemical agentsbeing added to thelatter which together with the complex combination result in solublereaction product.

The process of the chemical reaction or transformation according to thepresent invention is mainly a physical process, that is to say a doubleor mutual reaction or transformation is attained by employing adissolving process in combination with a simultaneous precipitatingprocess. In order to properly carryi iiut such chemical reactionijortransformation according to the present process, the imageformingsub'stance, for which AgBr or AgCl is preferably selected, issubjected to the action of a solvent which possesses a strong solventaction for the said substance while the solution and the agent added tothe solvent, must be insoluble or only slightly soluble therein. Thefunction of the process may be best understood by an example with asimple solvent alan inthough this permits only a limited selection oftransforming possibilities.

For instance, if a silver chloride image is treated with ammoniummolybdate, which is dissolved in diluted ammonium hydroxide, the silverchloride will be dissolved in the ammonium hydroxide and transformedwith the ammonium molybdate into silver molybclate which is slightlysoluble in diluted ammonium hydroxide and 'pre- I cipitated in place ofthe former silver chloride image. In connection with this transformationand all hereinafter described transformations, the solvent is usedaccording to the present process not unnecessarily concentrated but 'ina dilution which effects a good but not too quick solution of the imagesubstance, in the above case a solu-, tion of about 10% ammoniumhydroxide. The transforming agent, for instance, ammonium molybdate isadded thereto usually concentrated.

The required exact addition is due to the fact that M the precipitatingprocess, whose speed. depends on the concentration of the precipitatingagent, must take place more quickly than the dissolving process. A toohigh concentration of the precipitating agent is therefore notdetrimental but only a concentration which is too low because in thiscase the precipitation does not take place, as is required,spontaneously at the place of the image but only after the solution inthe bath. The proper concentration of the transforming agent musttherefore be determined very quickly so that no detail of thetransformation image may be lost otherwise the concentration of thetransforming agent must be increased.

According to the present invention, in order to transform the silverimage into other chemical products, complex combinations areadvantageously employed, which either are formed in.

'the photographic image by forming double salts or which possess thefeature of being contained in the silver halide, a process which will bedescribed more specifically hereinafter.

A formation of the kind of a double salt solution and its further useforchemical transformation according to the present process takes placein the following manner by way of example: The silver halide image isbathed in a diluted solution of about 2-5%, manganic thiocyanatewhereupon the silver halide becomes transparent to the extent of theformation of its complex combination. In lieu of the former transformedsilver halide image, a compound is obtained whichis capable of reactionand can be used for further transformation. By means of the thiocyanategroup cyanate reducing reactions may be carried out, as hereinafterdescribed, or the manganese may be used for oxidation processes bytransforming the same in the known manner by an alkaline of the. addedmanganic thiobath into a manganese dioxide image from which oxidationdye images can be produced.

However far more possibilities of reaction are given when using suchcomplex combinations which have been called formation hereinbefore,because by the same it is possible to finally transform in a most simplemanner the silver image into any desired chemical combination as will bedescribed hereinafter. Compared with the above loose addition, or doublesalt combinations, certain organic combinations possess the property ofcombining with metallic salts, preferably salts of silver, mercury,copper and lead, and form with the same very characteristic new complexcombinations. This property will be frequently found in the case of thecarbamide or urea group and the thio-urea group. For instance guanidineH2N.C(NH) .NH2 with silver salts combine to form a new member silverguanidine HzN.C(NH) .NHAg. I

. otherwise do not produce an insoluble combination with silver, maytherefore also form with the photographic silver image a water-insolublecombination, which may then be used in any desired manner for furtherchemical transformation.

. If, for instance, a silver image is bleached in the known manner toform a silver chloride or bromide image and the latter' is bathed in athiosiamine solution of to 1% to which is added sodium phosphotungstatein a concentration according to the above-mentioned indications 2.silver phosphotungstate complex will be precipitated as the silverhalide passes into solution in the thiosiamine. This precipitated matteris a means for fixing basic dyes in a waterproof and light fast manner.Therefore it is possible to obtain dye images by bathing thephosphotung'state image in a solution of a basic dye and subsequentlyremoving the phosphotungstate image by treatment in a solution ofthiosulphate.

If in lieu of the sodium phosphotungstate another salt is added to thethiosiamine bath, this silver salt will be .quantitatively precipitatedin an insoluble form in a few seconds in lieu of the former silverhalide image.. By adding potassium ferrocyanide, a silver ferrocyanideimage is obtained which may be transformed in the known manner intotoning images etcetera. In view of the character of these silver complexes to yield with substances insoluble combinations, it is possibleto produce photographic images also with these substances andsubsequently to carry out chemical processes, 'which have not beenattained heretofore with the common photographic baths. For instance or-'ganic sulphonic acids are precipitated in the a presence of the saidcomplex formers as comamino-3-6-disulphonic acid on a silver bromideimage, a corresponding complex silver image is produced in its place.Most of the azo dyes possess as components organic sulphonic acids andtherefore azo dye images of an unlimited variety can be produced by thetransformation of the silver image into the same and by a subsequentcoupling bath with diazo components.

The insolubility of the respective complex silver combinations dependson the choice of the respective complex formers, and therefore in manycases preferably dialkylated thio-ureas, thiosemicarbazide, guanidine orsimilar suited substances are used in place, of thiosinamine.

Instead of adding to the complex-former that group (for instance, N03)which is to be combined with the silver image in the form of a salt (forinstance, NaNOa), in order to precipitate it at the place of the silverimage in the described manner, it is possible to combine the desired"groups directly with the complex-former (for instance, guanidinenitrosylsulphuric acid) whereby it is directly embodied in the silverimage without any process of dissolution.

In addition to these complex silver images also image intensificationsmay be directly produced by subsequently treating the bluish toned ordyed silver image in an alkaline bath. Silver sulphide is formed by thealkaline bath, which former intensifies the blue image and at the sametime renders it black, if a readily decomposable sulphur compound isemployed as complex-former.

Of these complex-formers especially the thiocarbamide possesses acharacteristic which in a purely physical way can be used for producingphotographic dye images. If in addition to the thiocarbamide a silvercompound is used which is quite insoluble in the same and ifconcentrated thiocarbamide of about,5% is used, the image will betransformed into "a transparent caoutchouc-like substance. Thelattercloses the pores of the gelatine at the image-places in a watertightmanner as if the same had been treated with resin. After the image hasbeen dried, it is placed into an acidic dye-solvent and at the same timea silver-compound'is taken which does not show any causticity for dyes.In view thereof the dye is fully repelled at the places of the complexsilver image and, by its imbibition into the remaining part of thegelatine, a negative dye image is produced compared with the initialimage.

What I claim is:

1. Process for toning silver images consisting in transforming thesilver into silver halide, and subjecting the transformed image to abath containing a complex forming solvent for the silver halide of thegroup of thiosinamine, thiourea, thiosemicarbazide, guanidine andcontaining also a reagent which immediately forms an insolubleprecipitate with the silver complex, but which does not react with thesilver halide.

2. Process for toning silver images consisting in transforming thesilver into silver halide and subjecting the transformed image to a bathcontaining a complex forming solvent for the silver halide of the groupof thiosinamine, thiourea, thiosemicarbazide, guanidineand containingalso azo dye components having a sulfonic acid grouping.

FRIEDRICH LIERG.

